Have a very similar filter/problem over here. Was getting a little bit of sand shooting back into the pool after backwashing and rinsing. Was going to let it go until next season, but my skimmer was leaking, so had to drain anyways. Used the stickied hose cleaning method for about an hour and got a whole bunch of junk out, then realized my pvc pipe leading to my laterals has a crack running down it. Now I'm going to order a new pipe and laterals and probably get some new clean sand in there while I'm at it. One problem just leads to another. Hope your Heyward behaves better than mine.